In an Omega 564 there are 56 parts involved in the winding mechanism. 35-plus of them can contribute to a problem. Sticky old lubricants (very common), broken mainspring (common), rust (possible), broken jewels (not uncommon), long synthetic sweater fibers wrapped around a wheel (more common than you'd think), etc. As John said, without tearing the watch down there's no way to guess.
I have one Constellation waiting in line right now that's showing that behavior. I returned another Constellation earlier this week that would auto-wind but wouldn't stem-wind - it turned out that the crown wasn't pushed all the way in.
Check your private messages.
Glen